“Game of Thrones” will welcome a bevy of new castmembers in its third season, George R.R. Martin announced at Comic-Con on Friday.

After a trailer reviewing what happened on the second season of the show, the author of the fantasy novels ushered in a video showing more than a dozen new characters, highlighted by Diana Rigg as Lady Olenna Tyrell. Also known as “The Queen of Thornes,” she is the grandmother of Margaery and Loras Tyrell (Natalie Dormer and Finn Jones).

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“Clearly I have to start killing some of these characters to make room for the new ones,” Martin joked, noting that the HBO show already had one of the biggest casts on television.

David Benioff and D.B. Weiss, "Game of Thrones" showrunners, could not appear at Comic-Con as they have already started filming season three in Iceland. Martin said that they would be directing episodes this season as well, adding to their writing and producing duties.

Other news castmembers include Mackenzie Crook (above) as Orell, Clive Russell as Brynden “The Blackfish” Tully and Nathalie Emannuel as Missandei. Kerry Ingram, Paul Kaye, Thomas Brodie-Sangster, Ellie Kendrick, Richard Dormer, Kristofer Hivju, Philip McGinley, Tara Fitzgerald, Tobias Menzies and Anton Lesser will also join the cast.

"Game of Thrones" season 3 is set to premiere on March 31, 2013.